Ankle Foot Orthosis Using Shape Memory Alloys for Addressing Drop Foot
Inactive Publication Date: 2015-10-15
UNIVERSITY OF TOLEDO
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Benefits of technology
This patent describes a new design for an articulated passive ankle foot orthotic (AFO) that uses a single-sided superelastic shape memory alloy (SMA) hinge. The SMA hinge helps to prevent instability and hypermobility during walking, by providing the necessary motion to inhibit drop foot. The design is compact and lightweight, and has high energy density, making it an effective solution for weight reduction and minimization of system complexity. The use of SMA also provides natural elastic properties close to body tissues, which makes the device more comfortable and biocompatible.
Problems solved by technology
Drop foot results in the forefoot slapping the ground at heel strike and dragging the toe during the swing phase.
Affected people tend to have a labored, unsafe gait and suffer from fatigue which further reduces their speed and efficiency.
Without treatment, drop foot can cause severe injuries in the affected limbs and other limbs which are required to compensate for the deficiency.
Although both physical therapy and surgery have shown some biomechanical benefits, disadvantages preclude them as acceptable treatments for all patients.
Although these light orthosis prevent drop foot, walking is still difficult with them because they do not provide the required torsional stiffness of an ankle during normal gait.
These AFOs cause too much resistance to plantarflexion, inhibiting ankle motion throughout the loading response.
They also lead to disuse atrophy of the ankle flexor muscles by completely restricting the ankle movement.
Another common complaint among AFO users is that they are so uncomfortable that the user often forgoes the AFO.
Further, many users require modification to their footwear to accommodate the bulky AFOs currently available.
Although these devices are lightweight and durable, walking stability and adjustment of compliance are two main issue to be considered.
Method used
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[0028]Superelasticity is the featured ability of some materials to recover large amount of deformation without any residual strain. Shape memory alloys (SMAs) exhibit this property at specific temperatures due to a solid-solid phase transformation which occurs in these materials under mechanical loading.
[0029]While any method of fabrication may be used to produce the SMA hinge, the inventors relied on Additive Manufacturing as generally described in the following publicaitons: HABERLAND, Christoph, Additive Manufacturing of Shape Memory Devices and Pseudoelastic Components. SMASIS2013-3070, and HABERLAND, Christoph, Visions, Concepts and Strategies for Smart Nitinol Actuators and Complex Nitinol Structures Produced by Additive Manufacturing. SMASIS2013-3072.
[0030]As shown in FIG. 1, during powered plantarflexion, an internal stress is induced in SMA which causes the material to be loaded. When the foot leaves the ground during the swing phase, the stress is no longer applied and the...
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An ankle foot orthosis (AFO) is provided to address the drop foot irregularity. In two introduced embodiments of the device, a shape memory alloy (SMA) component is loaded during powered plantarflexion. The SMA would then enable the AFO to lift the foot during the dorsiflexion, when the foot drops. The AFO offers a compact and lightweight structure, however, while still providing the patient the desired lift in during dorsiflexion.
Description
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH[0001]This invention was not made with any federally sponsored research or development support.TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION[0002]The present invention relates a solution for treating people with drop foot.CROSS REFERENCE TO RELATED APPLICATIONS[0003]This application claims the benefit of U.S. provisional patent application Ser. No. 61 / 977,130 filed Apr. 9, 2014.BACKGROUND OF THE INVENTION[0004]Drop foot is a neuromuscular disorder described by the inability of the patient to dorsiflex (raise up) the front portion of their foot. Drop foot may be caused by various reasons including stroke, diabetes, multiple sclerosis, etc. The insufficiency is physically characterized by weakness or paralysis of the muscles around the ankle so that the patient cannot dorsiflex, but is still able to plantarflex (push down) the foot. Drop foot results in the forefoot slapping the ground at heel strike and dragging the toe ...
Claims
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Login to View More IPC IPC(8): A61F5/01
CPCA61F2005/0132A61F5/0127A61F5/0113
InventorELAHINIA, MOHAMMAD H.GORZINMATAEE, MORTEZAANDANI, MASOOD TAHERI
OwnerUNIVERSITY OF TOLEDO